Old Day and Night Furnace Ignition Issue

I have an older home in Burbank, CA with a Day and Night furnace/AC system on the roof. We've been in the house many years and the system has been pretty reliable except for an intermittent ignition problem, usually when it's raining or damp out. I've had it serviced a few times, most recently the burners were cleaned and the gas valve was replaced. I have changed out the spark electrode and ignition module parts a few times over the years and that seemed to solve the issue for a season or two. Last weekend, in the middle of a few days of rainy weather (during a few dry hours) after the furnace wouldn't kick on all day, I went up on the roof and cleaned the electrode and metal that it arced to (which had rusted a little) with some steel wool. After I reassembled it and turned it back on, the spark looked fine and it lit right up. Unfortunately this morning it wouldn't come on until an hour after I'd turned it on, as I was walking out the door for work. I figure I'll go ahead and replace the ignition module and electrode again (see links) but I'm wondering what else I should look at? What would a pro do? Is this system just at the end of its life? I really don't want to spend 8-10k for a replacement, especially since we only use it for a few months of the year, but I would like to have heat when we want it - rain or shine. Take the cover off the burner compartment of the furnace. Obtain the model of the furnace off the rating plate in the burner compartment and post it here. Observe the sequence of events that occurs at the furnace when you turn up the thermostat and post that sequence of events in order and in detail. Thanks for the reply. Will do this w/e. I predict though, that because I'm watching it it will function just fine. I suppose what I need to know is 1) is the pilot lighting consistently when the thermo is turned on and 2) the time between the pilot igniting and the burners firing up (when the main gas valve opens). If the pilot fails to light sometimes, then changing out the electrode igniter modules may have an effect but if that's not the problem.... thermo-coupling needs to be changed? You need to relate ALL the things that happen in the ignition sequence. The more you leave out or the more vague you are, the less we can help. ..and I will do that asap but I can't get back up on the roof until Saturday at the earliest. In the meantime, I'm trying to understand what should happen and what might be wrong. Since I know very little about these systems, I'm hoping to learn a bit by asking questions. This morning it took a while but the heat did come on. I'm beginning to suspect that the temp sensor to the gas valve. It makes sense that when it's cold and damp it takes forever for it to finally realize the pilot is lit.... I usually turn the thermo low or even off overnight so on Saturday morning, I'll get up on the roof and open up the unit. Then, have my wife turn the thermo on while I observe the sequence of events. As predicted, it worked fine while I was watching but here's the info requested: Model #: Day and Night/Carrier 585B042100 YACR Link to pics of unit Observed at about 4pm, fairly warm afternoon (~65F) sun hitting unit: thermo in demand, switch turned to HEAT electrode starts sparking immediately but it takes about a minute for the pilot to ignite after pilot lights, spark stops immediately main gas valve opens 45 seconds later burners light blower comes on about 45 seconds later after running for a couple of minutes, switched moved from HEAT to OFF main gas valve shuts off immediately and burners go out blower stops about 30 seconds later After a few minutes I had my wife turn the switch to HEAT again. The above cycle repeated but the pilot lit much more quickly, in less than 30 seconds and the main gas valve opened in about 30 seconds. I suppose I needs to do this on a cold morning but I was surprised at how long it took the pilot to light the first time on a warm afternoon. I'm thinking that replacing the igniter components as I have done in the past will solve the issue. It looks like either the spark isn't hot enough to light on cold damp days or the gas flow to the pilot ignition is insufficient. I suppose the thermocouple could also take a long time to tell the main valve to open when it's cold so maybe replacing all three components (electronic ignition module, electrode, and thermocouple unit) would be the best bet. Opinions? You don't have a thermocouple, you have a Carrier 3-wire intermittent pilot burner assembly. On a call for heat the spark generator and the pilot gas valve are energized. The spark lights the gas and then it heats up a bi-metal (thermostatic) switch in the assembly that cuts off the spark first and then closes the circuit to the main gas valve. That you have such a long time between spark initiation and actual pilot flame tells me that you either have a leak in the pilot burner tubing OR the orifice in the pilot burner is semi-fouled and not allowing the full flow of pilot gas. Seattle Pioneer should respond with his take. He has way more experience with these than I. That unit has the 5 wire pick n hold gas control EF32CW183 and the 732 pilot assy. The pick and hold feature is part of the safety system so the gas can't possibly turn on if the pilot isn't lit. So first the pilot has to pick and then when the bi metal warms up and closes the circuit the gas control will hold and then come on. Due to the age of the unit, you have to pull the top cover off the unit and inspect the heat exchanger for cracks or holes. This is done by a pro who knows what to look for. carry on... The most common problem with a Carrier 3 wire pilot is that the pilot burner and pilot orifice are dirty and need to be cleaned. When dirty, sometimes the pilot wont light and you will see thge spark continuiong to work. More commonly the pilot lights but not the main burners. This is because a poor pilot flame wont get the bimetal temperature sensitive switch hot enough to turn on the main burners. Cleaning the pilot burner and orifice are routine maintenance that should be done once per year to avoid problems. Do that now and it's pretty likely you will be back in business. Thanks for your reply! I believe once the pilot lights, the burners fire up pretty quickly. It's been working fairly well lately. Seems the more we use it, the more reliable it gets. How should I clean the pilot burner? It appears to be pretty clean from the outside. Should I remove the pilot gas tube from the main valve and use a compressed air can to blow out the tube (from the valve end toward the burner end) ? To clean the pilot burner-- Remove the two screws that hold the pilot burner to the chassis. Gently bend the pilot tubing to bring the pilot tubing out so you can work on it. Use a wrench to loosen the brass fitting that holds the pilot tubing to the pilot burner then pull the pilot tubing from the pilot burner. The pilot orifice is at the end of the pilot tubing -- it may fall in your hand when you remove the pilot tubing. Clean the hole in the pilot tubing with a wire ferom a wire brush. Use aq wire brush and some air to clean out any debris from the pilot burner. Reassemble the pilot burner aqssembly. This is routine maintenance that should be done every year or two to avoid problems. The tube is easy to remove from he main gas valve, then I don't have to bend it to get to the pilot burner. I've done that in the past when changing out the electrode. Is that not recommended? By all means disconnect the pilot tubing at the gas valve if you prefer. I'd soap out the fitting when you reinstall it to be sure it's not leaking. Well, here I am again one year later with problems again. I did the routine cleaning as suggested and the pilot flame lights quickly and reliably but the main burners never fire up. So, either the sensor is not sending a signal to the main valve or the main valve is not responding. How can I determine which is the case? If it's the sensor, I can DIY as long as I can find the part. If it's the main valve (which was replaced only a few years ago and the previous one worked for 25+ years), I'd feel more comfortable having it done professionally. Go ahead and have a pro do it. The bi metal pilot may not be making, and that may be the reason the main valve won't open. You need to test for 24 volts at several locations to determine if the pilot safety isn't making all the way. Also, have him take the top of the unit off to inspect the heat exchanger for holes while he's there. OK, thanks for the reply. Service has been scheduled for Friday. I'll post the results. If anyone else should have other DIY test suggestions, I'm open to hearing them. I can always cancel for Friday... Unplug the pilot harness. Using a jumper, install into the yellow and green, after pilot lights remove jumper and install in the white and yellow. This will open the gas valve for burner gas. This will prove if it is the pilot or not I'd like to try that but I'm a little confused. Are you saying initially disconnect the white wire from the pilot until lit then connect the white and disconnect the green? Can you explain what each wire does? Most 3 wire pilots have molex plug. Separate the plug so the pilot is not connected. On the side you seperated the pilot from insert a jumper into the holes that feed the yellow and green wires. After the pilot lights remove jumper and insert in the holes for the yellow and white. Thermostat must be calling for heat. Green/yellow..normally closed. Yellow/white normally open if in doubt let the tech check Friday My system is old and doesn't use molex connectors but I think I understand now. What I am doing effectively simulates the correct action of the sensor. After disconnecting all 3 pilot wires, at the valve I jumper green/yellow for pilot ignition then open g/y but removing the jumper and close y/w with a jumper to activate main the valve. I could also check the circuit continuity with a meter of the pilot wires during the procedure. I should see green/yellow open and yellow/white closed after the pilot is lit, right? Do not jump at valve , I think this May be more difficult than I thought given you have no molex plug. Maybe wait for teach. I would hate to see damage caused. So, pro replaces gas valve ($$$). System works fine....but next morning doesn't light. He comes back. Pilot is not lighting reliably (it was before I called him). He adjust spark point. Once again, it works....until this morning when it won't light once again. He's due back here in 30 minutes. UPDATE: well, it's lighting again. I watched as he adjusted the ignition spark gap and tested ignition multiple times. So tomorrow, it it doesn't light again I'm thinking the spark isn't strong enough and I should change the ignition module. I said that to the tech but he didn't think it was necessary... I guess it's time to think about retiring this ~45 year old system ... Sounds like you have a parts changer? Oh well

Related Posts:

• 
  Moncrief furnace blower issue
  
  Moncrief furnace blower issueI have an older York Moncrief model L-100-E Series # 3. I came home from work today and I noticed my house was a bit chilly. I turned the furnace up 2 degrees and it c...
  


• 
  Miller furnace problem
  
  Miller furnace problemI just bought a house with a 1996 Miller MMHA-070ABHR-05 furnace.The furnace starts,inducer fan runs and the burner comes on,but as soon as the blower kicks on it runs for 10...
  


• 
  Pt cruiser electrical issue
  
  PT cruiser electrical issueHey all, I have a 2002 PT cruiser. Problem first occurred about a week ago. I went to lock the vehicle with the key fob and the doors didn't automatically lock like usua...
  


• 
  Oil furnace troubleshooting
  
  Oil Furnace TroubleshootingI have a Thermopride OL5-85 oil furnace that is running periodically but is shutting off prematurely well before reaching the desired heat level. The thermostat appears...
  


• 
  My nordynefrigidaire furnace wont ignite and fire up
  
  my nordyne/frigidaire furnace won't ignite and fire upHey doityourself forum... I'm brand new to this forum and would love to receive some much needed help with my home furnace. I have a NORDYNE/F...